Waste water filtration tank

ABSTRACT

A waste water filtration tank receives waste water under hydrostatic pressure. The tank collects solids using a filter screen. When the screen becomes clogged with collected solids, liquid is forced into a float chamber which contains a float. As waste water collects in the float chamber, the float rises, as do a beam member and a pair of rod members to which the float is attached. When the float reaches a predetermined level, cams contained on the rising rod members act on spring-loaded latches, opening the latches and permitting a spring loaded sleeve and reservoir gate to rise, opening the reservoir outlet. Accumulated solids are then drained from the reservoir and the backwash from the screen chamber also clears the clogged screen.

This application is the U.S. national phase application of PCTInternational Application No. PCT/GB00/01434 filed Apr. 14, 2000.

FIELD OF THE INVENTION

The present invention relates to a waste water filtration tank for thetreatment of raw waste water.

BACKGROUND OF THE INVENTION

Before waste water can be passed to processing plants such as watertreatment facilities, all the solid waste within the effluent must beremoved. It is known to use filtration tanks in order to remove suchmaterial, with the waste material being separated from the water beforethe water is either passed on for further processing or else, in someinstances, discharged back into the river or sea. Other known methods oftreatment include sand filtration and chemical treatment of the liquidto remove impurities.

SUMMARY OF THE INVENTION

It is the aim of the present invention to provide an automatic wastewater flushing system which filters out solids from the effluent beforeautomatically removing said solids from the tank, thereby allowing thefiltration to be carried out with the minimum of supervision and alsoremoving the need for the filtered solids to be discharged manually.

According to the present invention, there is provided a waste water tankfor the filtering of solids from effluent, said tank comprisingfiltration means and automatic discharge means, wherein said dischargemeans discharges the filtered solids when said filter reaches apredetermined degree of contamination.

Preferably, said tank further comprises an inlet and first and secondchambers, said filtration means being located between said inlet andsaid first chamber. Preferably, said effluent enters said inlet underhydrostatic pressure.

Preferably, said tank further comprises a reservoir which communicateswith said inlet and each of said first and second chambers.

Preferably, said reservoir has a discharge outlet which moves betweenopen and closed states under the action of said discharge means.

Preferably, said filtration means is a mesh screen adapted to preventsolids of a predetermined size from entering said first chamber fromsaid reservoir.

Preferably, said tank is adapted so that liquid flows into said secondchamber from said reservoir when said screen reaches said predeterminedlevel of contamination.

Preferably, said discharge means comprises a float located within saidsecond chamber, a gate covering said outlet, and operating means for theoperation of said gate, wherein said float acts on said operating meanswhen the level of liquid in said second chamber reaches a predeterminedlevel.

Preferably, said operating means comprises a pivotable beam member,first and second rod members having first and second cams attachedthereto, a flanged sleeve member attached to said gate, and a lockingmeans, wherein said beam member and said first and second rod membersare attached to said float, and wherein said beam member and said firstand second rod members are adapted to communicate the movement of saidfloat to said gate. Preferably, said operating means further comprisesbiasing means which forces said gate into the open position.

Preferably, said locking means comprises a pair of spring-loaded latchesadapted to move between open and closed positions, said closed positionbeing when said latches act on said flanged sleeve member and said openposition being when said latches move away from said sleeve member underthe action of said first and second cams, said gate opening under theaction of said biasing means.

A preferred embodiment of the present invention will now be described,with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a projected view of the filtration tank according to thepresent invention, the side wall of said tank having been removed forillustrative purposes;

FIG. 2 shows a side elevation of the tank, with fluid flow directionshighlighted;

FIG. 3 shows a plan view of the tank as seen in FIG. 2;

FIG. 4 shows a rear view of the tank as seen in FIGS. 2 and 3;

FIG. 5 shows a front view of the tank as seen in FIGS. 2 to 4;

FIG. 6 shows a projected cut-away view of the tank as seen in FIGS. 2 to5; and

FIG. 7 is a detail view of the sluice mechanism as seen in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, FIG. 1 shows a waste water filtration tank 1with a side wall panel removed for illustrative purposes. The tank 1 hasan inlet chamber 3, and a screen chamber 2 which contains a screen 7.The unfiltered effluent is pumped into the inlet chamber 3 via pressurefrom a generated head through inlet flange 11. The head can either begenerated by a pump or by gravity. The effluent flow fills the inletchamber 3 and the reservoir 8 until it reaches a predetermined levelwhereupon in begins to pass upwards through the screen 7 into the screenchamber 2. As the effluent passes through the screen 7, solid residue istrapped in the reservoir 8 and cannot pass into the screen chamber 2.Due to the pressure generated in the head, the level of filtered liquidwhich enters the screen chamber 2 continues to rise until it begins tooverflow 9 into an overflow chamber 4, which can be seen in FIGS. 2 and3. The filtered liquid then passes out of the overflow chamber 4 viaoutlet 10 to be discharged for further treatment or else into a sea orriver area.

The more solids which are filtered by the screen 7, the more blocked thescreen 7 will become, thus restricting the flow of liquid through thescreen 7 into the screen chamber 2. With the restricted flow through thescreen 7, a back pressure is created in a stilling chamber 5 connectedto the reservoir 8. As the screen 7 continues to clog, the back pressureincreases in the stilling chamber 5, raising the level of liquid in thestilling chamber 5 until it begins to overflow into a float chamber 6.

The float chamber 6 contains a drum float 13 which will begin to rise asliquid enters the chamber 6. The float 13 is part of a mechanism whichcontrols the automatic operation of a sluice gate 17. This gate controlmechanism alleviates the need to flush the tank 1, as the tank lautomatically flushes itself when solids have blocked the screen 7 to acertain degree.

As shown best in FIG. 1, the gate control mechanism consists of apivoting beam 14 to which the float 13 is attached. Also attached to thebeam 14 at the opposite end from the pivot are a rod member 15 and apair of secondary rod members 19, with the rod member 15 passing downthrough a sleeve 20. The sleeve. 20 has a flange 16 around itscircumference, and marries with the top of a sluice rod member 18 whichis connected to a sluice gate 17. The sluice rod member 18 is acted onby a compressed spring (not shown) which acts upwards on the sluice rod,the sluice rod acting on the sleeve 20.

As the rise in fluid within the float chamber 6 lifts the float 13, thefloat 13 raises the beam 14,-which in turn lifts the rod member 15 andthe secondary rod members 19. The pair of secondary rod members 19 eachpass through spring-loaded latches 21 which hold the sleeve 20 inposition via the flange 16. The latches 21 each have an aperture 22through which the secondary rods 19 pass. These apertures 22 have atapered inner surface 22 a which is acted on by a cam (not shown)attached to the secondary rod 19. As the combination of the float 13 andbeam 14 lift the secondary rods 19 to a predetermined level, the camsact on the respective inner surfaces 22 a of the latches 21, therebypushing the latches 21 outward against their springs (not shown). Theoutward movement of the latches 21 releases the flange 16 of the sleeve20, sending the sleeve 20 and sluice rod 18 swiftly upwards under theforce of the compressed spring. The rapid upward movement of the sluicerod 18 then opens the sluice gate 17, allowing the solid residue andfluid trapped in the reservoir 8 to be discharged.

As the reservoir 8 is discharged through the sluice gate 17, the levelof fluid in the screening chamber 2 will quickly drop, thus backwashingthe screen 7 to remove any solids on the underside. At the same time asthe sluice gate 17 is opened, a dump valve (not shown) within the floatchamber 6 opens, thus emptying the float chamber 6 at a controlled rate.As the float chamber 6 empties, the weight of the float 13 causes boththe float and beam 14 to lower. With the lowering of the beam 14, therod member 15 pushes the sleeve 20 and sluice member 18 down against thespring until the tapered flange 16 reengages with the latches 21. As thesleeve 20 lowers, it also lowers the sluice member 18 to compress thespring and close the sluice gate 17 against the flow of fluid throughthe inlet flange 11. The mechanism then automatically resets and beginsthe filtration cycle again

Thus, the filtration tank 1 provides a filtration mechanism whichfilters the incoming effluent until such time as the filtering screen 7becomes blocked. Then, without the need for operation by an operator,the mechanism will automatically discharge the filtered solids and beginthe cycle again. Thus, the mechanism can operate with the minimum ofsupervision, and without the need for any manual intervention.

Modifications and improvements can be incorporated without departingfrom the scope of the invention.

What is claimed is:
 1. A waste water filtration tank for filteringsolids from effluent, the tank comprising: an inlet; first and secondoutlets in fluid communication with the inlet; a filtering screenlocated between the inlet and first outlet and having an outlet side andan inlet side; flushing means adapted to backflush filtered liquidthrough said filtering screen from said outlet side and out through saidsecond outlet when said second outlet is opened; and urging means foropening said second outlet, the flushing means comprising: detectingmeans for detecting a predetermined degree of contamination of thefiltering screen, and latch means coupled to said detecting means andsaid urging means said latch means responsive to said detecting means torelease said urging means and cause said second outlet to open.
 2. Thetank of claim 1, wherein the detecting means comprises: a first chamberin fluid communication with the inlet; a second chamber separated fromthe first chamber by a barrier means; and a float positioned in thesecond chamber and adapted to actuate the latch means.
 3. The tank ofclaim 2, wherein the float actuates the latch means when the level ofliquid in the second chamber reaches a preset level.
 4. The tank ofclaim 2, wherein the detecting means further comprises a beam memberconnected to the float, the beam member pivoting under the action of thefloat to actuate the latch means.
 5. The tank of claim 2, wherein theflushing means further comprises a dump valve located in the secondchamber.
 6. The tank of claim 1, wherein the flushing means furthercomprises a sluice gate, the sluice gate being movable between first andsecond positions which correspond to closed and open states of thesecond outlet, respectively, the sluice gate moving to the secondposition from the first position under the action of the urging means.7. The tank of claim 6, wherein the latch means comprises at least onelatch and a biasing means biasing the latch into contact with the sluicegate, wherein the latch retains the sluice gate in the first positionuntil the latch is acted upon by the detecting means.
 8. The tank ofclaim 1, further comprising an overflow chamber located between thefiltering screen and first outlet.
 9. The tank of claim 1, wherein theliquid pressure on the inlet side of the filtering screen increases asthe degree of contamination of the filtering screen increases.